Phase shift control for three element electron tubes



Aug. 3, l 93 7.

F. MOSELEY 2,088,659 PHASE SHIFT CONTROL FOR THREE ELEMENT ELECTRON TUBES 'Filed July 8,1933 2 Sheets-Sheet 1 INVENTR v fife/V015 L, Noam/5y.

ms ATTORNEY.

Aug. 3, 1937. F. L. MOSELEY 2,088,659

PHASE SHIFT CONTROL FOR THREE ELEMENT ELECTRON TUBES Filed July 8, 1933 2 Sheets-Sheet 2 JJUUMMMJ INVENTOR 576N015 L, 705ELY.

and Leas shownin Figs.

to l and In, A. c.

Patented Aug. 3, 1937 4 UNITED STATES PHASE SHIFT CONTROL FOR THREE ELE- lHENT ELECTRON TUBES Francis L. Moseley,

Sperry Gyroscope Company, Inc.,

Brooklyn, N. Y., assignor to Brooklyn,

N. Y., a corporation of New York Application July a, 1933, Serial No.

In Great Britain January 11, 1933 8 Claims.

This invention relates to the graduated control of the phase on grid of three element electron or thermionic tubes such asgrid controlled gas filled rectifier tubes by which the output is smoothly and readily varied both in magnitude and direction. One application of my system lies in thepositional control of objects by such tubes and has application to so-called follow-up systems and remote control systems for rotary objects by means of reversible electric motors. Such a system is best controlled by dynamically and progressively shifting the phase on the grid of the grid-glow tube or tubes and one object of the present invention is to provide a means of obtaining dynamic phase shift without the use of complex bridges or similar circuits. A further object is to secure the simultaneous graduated control of two grid-glow tubes in a push-pull fashion, so that as the rectified output of one is increased the output of the other is decreased.

Although the present invention is herein shown as applied to a follow-up system for gyro com- 7 passes and the like, it is not intended that it be limited thereto inasmuch as certain modifica- 5 tions and changes may be made without departing from the original spirit of the invention or the scope of the appended claims.

Referring to the drawings, Fig. 1 is a schematic wiring diagram showing the general principles of my invention.

Fig. 2 is a series of wiring and vector diagrams illustrating the mode of operation.

Fig. 3 shows one application of my invention wherein the present invention is used to control a double wound reversible D. 0. motor as part of a follow-up system for a gyro compass.

At the controlling or sending element is placed some means for transmitting a voltage depending upon relative displacement between the sending and receiving or following elements. A simple form of such a transmitter may comprise a variable gap or variable flux transformer T1. As shown, one portion ll of said transformer comprises three legs and is preferably mounted on the following element, while the other portion II,

which is mounted on the sensitive or sending element, comprises merely a strip of soft iron.

The windings may all be placed on the member ll ifdesired and alternating current may be supplied to either the central winding as shown in Fig. 3 or to the two opposite outer windings L1 it will be evident that as I i is moved with respect signal voltages are generated 1 and 2i. In either case of variable magnitude and versible phase position). as shown in Fig. 2A, that put e; is zero, but when it is moved in either direction as shown in Fig. 23, a voltage will be induced in 1a. The phase (direction) of this induced voltage will be determined by whichever flux o1, 4:: (from L1 or La) predominates but'there is no graduated shift of phase but merely a reversal as the resultant voltage passes through zero. The magnitude e. will be dependent on the difference of said ment II is moved to the right, as shown in Fig. 2C, the voltage es is of opposite phase to that in Fig. 2B. The voltage es induced in L3 is communicated to a suitable transformer coupler T2, preferably having two secondary windings 1s and Le con nected in series so that when the point I is positive with respect to point 3, point 2 is negative and vice versa. If point 3 were directly connected to the cathodes I3, l3 of one or more electron tubes such as grid-glow tubes V1 and V2, it is clear that if a common A. 0. supply be connected to the plates of said tubes and to signal transformer T1, said tubes would be turned fully direction or sign (1e- Tfhen ii is positioned is, centrally, the outfluxes. l Thus when elevoltage in Le. Such a system, however, does not give satisfactory operation and it is the pur-- pose of the present invention to supply an improved means for progressively and proportionately, and preferably also oppositely, controlling the phase positions of the voltage supplied to the grid of said tubes. To effect this purpose I m. troduce between point 3 and the tubes a source 0 v of bias voltage preferably constant in magnitude though not necessarily so'and displaced in phase with respect to the plate supply 'to the tubes through an angle which may be, for example, Such a voltage may be readily secured by number of known means. For instance, in Fig. 1, I have shown the bias source as comprising an auto-transformer coil ii, the center point of whichis connected'to the cathodes l3, l3 and to one side of the supply, one end to point 3 through resistance l1 and the other end to the other side of the line and to a condenser li-also connected to point 3.

The points i and of windings L; and 14 are respectively connected through suitable resistances I! and I! to the grids ll and ll of said tubes to limit the grid current down through the transformer, while the plates are connected to DPP DK wndings. such as field windings F1 and phi ,00 said secondary winding v 5 the dotted lines at 20 and also between the grids and the windings Lo and Lo as dotted lines 2i- In further explanation of the operation of how my system dynamically shifts the phase on the grids of the tubes, reference is had to Figs. 2A, B and C. With no signal es in Fig. 2A, the presence of the 90 A. C. bias voltage es will cause tubes V1 and V2 to furnish equal rectified output currents I 1 and I to their load circuit, in this case, the fields F1 and F2. Since these windings are opposite, the resultant fluxes 1 and 4m are opposite and the motor torque will be zero. The plate voltage in each diagram is represented by line em or 2. In this case each tube will be passing approximately one half its maximum rectified current. If signal voltage e. is now supplied by T2 in one direction, the vector diagrams of Fig. 23 will apply in which the voltage across Ls is e., and across Ls is en and the resultant grid voltage on each tube V1 and V: is represented by diagonal lines egl and en respectively. The rectified outputs of the tubes are, therefore, unbalanced and are represented by output current lines Ipl and I: so that the amount Y and direction of the unbalance may be smoothly and progressively controlled by varying the magnitude and direction of the applied signal voltage (see Fig. 20). Resistance 22 may be used to limit the current carried by the motor, and condensers Cl and C: may be usedto filter the rectified current supplied to the motor.

Fig. 3'shows a more complete diagram in which vacuum tube amplification is used between the signal transformer and the grid-glow tubes. In .40 this case the primary winding of the supply transformer 25 is energized from one phase of the three-phase supply. There are three secondary windings 2G, for heating the cathode. of the amplifying valve 21, for heating the cathodes of the 45 grid-glow tubes V1 and V2 and 28 for power supply to said tubes and to the motor M. The

modulator or signal transformer T1 is supplied from suitable tapping points on the three phase system which are. obtained with the aid of the 50 potentiometer II; by this means the correct phase relation is obtained for the phase-shifting voltage, which is obtained from the modulator trans former Ti. and applied to the phase-shift transformer Ii after amplification by the vacuum 55 tube or valve 12. The secondary of the phase shift transformer ll consists of two separated equal windinga'which may be connected together through the condenser '2 in parallel with the secondary winding 33 of the transformer 34.

indicated by the 33 is center tapped so that the phase-bias voltage may be fed in between this center tap and the cathodes of the grid glow tubes V1 and V2. The phase-bias voltage is obtained from the output of potentiometer 05 II which is itself supplied with voltages by being connected across one of the three phase lines-and a point on the potentiometer 38 across the other pair of lines. The phase bias voltage is thus adjustable in phase by the potentiometer 3. and 70 in magnitude by the potentiometer II.

Inthis figure I have also shown a means for maintaining a tremor or hunting action in the follow-up system which has certain advantages, especially for gyro compass follow-up systems. 7 For this purpose the motor transformer 34 and will,

.of the right type to I object with respect to the state of slight oscillation by means hereinafter described which injects voltages into the phase shift transformer of the right nature to produce oscillations.

The current through tubes V1 and V: will vary at the low frequency at which oscillations of the motor are taking place. This current has a D. C. and an A. C. component. The varying current has, therefore, a low frequency component and a component of supply frequency modulated at low frequency. When tube V1' is passing a high current, tube V: is passing a low one. There will, therefore, be a difference of potential between the anodes which will have a low frequency component and a supply frequency component modulated at low frequency. Both will be applied to therefore, affect the circuit 32', a. The modulated supply frequency is shift the phase of the grid voltages and, therefore, to cause the tubes to maintain the oscillations of the motor. The whole action is, therefore, self-sustaining and does not require any external sources for voltages in the phase-shift circuit. The low frequency component also affects the output of the tubes to some extent, so that there is a general retro action or regenerative effect by which the tuned circuit 32, 33 controls the frequency of operation and, therefore, the frequency at which oscillations ,of the motor occur.

It is obvious that a duplicate circuit for full wave rectification could be provided, if desired, and also that the phase shifting principles of my invention may be applied to a singletube as well as to a pair of tubes.

In accordance with the provisions of the patent statutes, 1 have herein described the principle and operation of my invention, together with the apparatus which I now consider to represent the best embodiment thereof, but I desire to have it understood that the apparatus shown is only illustrative and that the invention can be carried out by other means. Also, while it is designed to use the various features and elements in the combination and relations described, some i of these may be altered'and others omitted without interfering with the more general results outlined, a nd the invention extends to such use.

Having described my invention, what I claim and desire to secure by Letters Patent is:

. 1. In a positional or follow-up control system for a reversible motor for positioning a driven position of a controlling member, means operated by said controlling member for producing an alternating E. M. F. varying in sense and in amount in accordance with the relative position of the controlling member and driven object, means for combining the E. M. F. with another alternating E. M. F. of different phase to ant between the grid and cathode of at least one grid-glow tube, forming part of a balanced cirdriven object, and coupling means included between the output. and input of said tube for maintaining a tremor in said motor.

2. A system according to claim 1 wherein the grid glow tube arrangement comprises a pair of il'ms ntsiood in a bala c cira itally I d-810W tubes to the grids form a resultant variable phase: E. M. It, and means for applying the said result- 3 of which are applied two variable alternating E. M. F.s under the control of the controlling member, vectorially at right angles to an added phase-bias voltage of different phase said phasebias voltage beingsupplied to said tubes in the same phase relation.

3. Means for driving an object into positional agreement with a controlling object comprising an inductive device, means operated by said controlling object for producing an electromotive force in said inductive device varying in direction and amount in accordance with the movements of said driven object, a pair of grid-glow tubes, a coupling transformer between said second means to supply opposite phases on the grids of said tubes, means for combining each output of said transformer with a substantially fixed voltage having substantially 90 bias for supplying differentially shifting phases to said grids with respect to their plates, a reversible motor driven by the output of said tubes for driving said driven object, and a regenerative coupling responsive to the output of said tubes and connected to the grids of said tubes for maintaining a tremor in said motor.

4. In a follow-up system for gyro compasses and the like, a control device, the output of which varies in magnitude and direction with departure of the follow-up from the sensitive element, a pair of grid-glow tubes, a coupling transformer between said second means to supply oppositephases on the grids of said tubes, means for combining each output of said transformer with a substantially fixed voltage having substantially 90 bias for supplying oppositely shifting phases to said grids with respect to their plates, and a reversible motor driven by the output of said tubes for driving said follow-up element and a regenerative coupling for maintaining an oscillatory phase shift of small magnitude to maintain a tremor in said motor.

In a positional or follow-up system for governing the speed and direction of a power motor from the output of a pair of glow tubes in accordance with the movements of a control member, the combination with an A. C. supply, an inductive device on said member powered from said supply,

. the output of which is governed in magnitude and sign by the position of said member, a pair of grid glow tubes also powered from said supply, and a transformer having its primary winding connected to said inductive device and the ends of its secondary winding respectively connected to the grids of said tubes for proportionally and oppositely shifting the phases on the grids with respect to that on the plates in accordance with the magnitude and sign of the output signal characterized by means for deriving a bias phase voltage for application in the same phase relation to both of said tubes, and means for supplying the grids with the combined bias voltages and signal.

6. In a. positional or follow-up system for governing-the speed and direction of a power motor from the output of a pair of grid-glow tubes in an A. C. circuit, a single phase A. C. supply, an inductive device powered from said supply, the output of which is varied in magnitude and direction, a transformer for inducing a pair of opposite voltages therefrom, impedance means connected to said supply for creating a substantially 90 bias voltage for application in the same phase relation to both said tubes, and means for combining the same with said signal opposite voltages, and applying the same respectively to the grids of said tubes.

7. In a positional or follow-up system for governing the speed and direction of rotation of a motor from the output of a pair of electron tubes by graduated phase shift of the voltage on the grids in an A. C. circuitfrom an inductive device adapted to produce a signal of variable magnitude characterized by combining with the signal voltage a substantially fixed yoltage for application to the grids of both-tubes in the same phase relation, said fixed voltage having a substantial phase displacement with respect to said signal voltage and supplying the resultant volt- 1 age to the grids of said tubes.

' 8. In a device for driving an object into positional agreement with a controlling object, cornprising a two part inductive device in which the balance between electromotive forces of opposite phase is disturbed in one direction or the other by relative movement of said objects, a pair of grid glow tubes having their inputs or grid circuits connected respectively to the opposite parts of said device and also havingoutput circuits, means for combining a fixed voltage with each input having a substantial phase displacement with respect to the signal voltages, said fixed voltage being applied to both of said grid glow tubes in the same phase relation, and reversible motive means controlled by the output of said tubes.

FRANCIS L. MOSELEY. 

